ORA-00937 not a single-group group function converted from SQL Server - sql

Question

I'm getting an ORA-00937 error when running the following ORACLE statement, I'm very new to Oracle (T-SQL is more my bag). I've converted a select statement previously written in SQL I'm at a loss as to why it's expecting a group by ... as all columns are sum'd. This is the converted select statement (I'm currently running/ testing these using SQLPLUS) :
select
round(COALESCE(
(COALESCE((select SUM((F_BOOK_DATES.BKD_ADATE_ENDS - F_BOOK_DATES.BKD_ADATE_START) * (60 * 24)) FROM F_BOOK_DATES
INNER JOIN F_BOOK_HEADER ON F_BOOK_DATES.BKD_FKEY_BK_SEQ = F_BOOK_HEADER.BK_SEQ
and EXTRACT (YEAR from F_BOOK_DATES.BKD_DATE_START ) = EXTRACT (YEAR from SYSDATE )
and EXTRACT (MONTH from F_BOOK_DATES.BKD_DATE_START ) = EXTRACT (MONTH from SYSDATE )
and EXTRACT (DAY from F_BOOK_DATES.BKD_DATE_START ) = EXTRACT (DAY from SYSDATE )
AND F_BOOK_HEADER.BK_STATUS NOT IN ('CX','TP')
AND F_BOOK_HEADER.Deleted <> 1
AND F_BOOK_DATES.Deleted <> 1),9999999999.99,0)
/sum(case when FAREALO.AllDayBooking = 1 then 1400 else
((FAREALO.LO_TIME_END - FAREALO.LO_TIME_START) * (60 * 24)) end) * 100),0),2) as "PercentUtilised"
from FAREALO
inner join F_LO_TYPE on FAREALO.LO_FKEY_LOT_SEQ = F_LO_TYPE.LOT_SEQ
where FAREALO.LO_BK_LOCATION = 1
and LOT_CBS = 1;
This is the SQL statement (that works) that I tried to convert above:
select
round(isnull(
(isnull(convert (DECIMAL(10,2),(select SUM(datediff(n,BKD_ADATE_START, BKD_ADATE_ENDS)) FROM F_BOOK_DATES with (NOLOCK)
INNER JOIN F_BOOK_HEADER with (NOLOCK) ON BKD_FKEY_BK_SEQ = BK_SEQ
AND DATEPART(YYYY,BKD_DATE_START) = DATEPART(YYYY,GETDATE())
AND DATEPART(MM,BKD_DATE_START) = DATEPART(MM,GETDATE())
AND DATEPART(DD,BKD_DATE_START) = DATEPART(DD,GETDATE())
AND BK_STATUS NOT IN ('CX','TP')
AND F_BOOK_HEADER.Deleted <> 1
AND F_BOOK_DATES.Deleted <> 1)),0)
/
sum(case when AllDayBooking = 1 then 1400 else
datediff(n,LO_TIME_START, LO_TIME_END) end) * 100),0),2) as PercentUtilised
from FAREALO with (NOLOCK)
inner join F_LO_TYPE with (NOLOCK) on LO_FKEY_LOT_SEQ = LOT_SEQ
where LO_BK_LOCATION = 1
and LOT_CBS = 1
Anybody see what I've missed?
Thanks
J

Answer 1

Here's the altered query which runs fine, after adding the MIN function:
select
round(COALESCE(
(COALESCE(MIN((select SUM((BKD_ADATE_ENDS - BKD_ADATE_START) * (60 * 24)) FROM F_BOOK_DATES
INNER JOIN F_BOOK_HEADER ON BKD_FKEY_BK_SEQ = BK_SEQ
and EXTRACT (YEAR from BKD_DATE_START ) = EXTRACT (YEAR from SYSDATE )
and EXTRACT (MONTH from BKD_DATE_START ) = EXTRACT (MONTH from SYSDATE )
and EXTRACT (DAY from BKD_DATE_START ) = EXTRACT (DAY from SYSDATE )
AND BK_STATUS NOT IN ('CX','TP')
AND F_BOOK_HEADER.Deleted <> 1
AND F_BOOK_DATES.Deleted <> 1)),9999999999.99,0)
/sum(case when AllDayBooking = 1 then 1400 else
((LO_TIME_END - LO_TIME_START) * (60 * 24)) end) * 100),0),2) as "PercentUtilised"
from FAREALO
inner join F_LO_TYPE on LO_FKEY_LOT_SEQ = LOT_SEQ
where LO_BK_LOCATION = 1
and LOT_CBS = 1;